In the document handling field there has been a longfelt need for a durable, water resistant envelope which is secure against unauthorized or inadvertent opening but which may be intentionally opened with great ease while minimizing potential damage to the contents therein.
Packages constructed from flexible materials such as laminates are well known. Similarly, packages constructed from "oriented materials" are common. Examples of such oriented materials include polypropylene, polyethylene, polystyrene and the like. Such oriented materials may have a high initial resistance to tear or tension breaks, but when once started they will tear with very minor resistance in a nearly straight line without the need for a secondarily imposed guideline of weakness.
Packages and pouches made from fully laminated plies are, of course, also well known and have been provided with opening devices of various sorts, as illustrated in U.S. Pat. No. 3,426,959, which issued to Jerome H. Lemelson on Feb. 11, 1969, and wherein a tear opening is defined by a line portion of the wall of the package, such line portion being of reduced thickness and having means disposed there along for effecting a controlled separation along the line portion.
Various means can be used to form a groove line, or line of weakness, to aid in the opening of packages. In one embodiment of the Lemelson patent, the use of a pair of thinned, parallel lines of weakness of the sides of a tear strip is disclosed. In U.S. Pat. No. 3,186,628 issued to William A. Rohde on June 1, 1965, probes were projected into the path of a thermoplastic film as it was being formed in order to weaken the material. Application of heated bars to areas of a material being formed could also result in areas requiring less tear initiation force. The prior art also illustrates other more sophisticated ways in which lines of weakness can be formed. One such disclosure is made in U.S. Pat. No. 3,909,582, which issued to William Edmund Bowen on Sept. 30, 1975, wherein a laser beam is used to score (i.e. provide a thin groove in) a layer of plastic film in a multilayer laminate. The score line functions as a line of weakness along which the laminate can be torn and, thus, functions as a package opening device.
With respect to tear initiating means, such is varied in the art. In one embodiment the use of a slit between two lines of weakness is disclosed in U.S. Pat. No. 4,139,643, issued to Diana L. Hicks et al. on Feb. 13, 1979. Another form of tear initiating is illustrated in U.S. Pat. No. 3,608,815, issued to Elmo L. Bunch on Sept. 28, 1971, in which a portion of the packaging material to be opened included a minutely expanded section of that material within an area that would ease the initiation and tearing of the package.
The conventional method for opening a sealed flap on a package, pouch or envelope is to manually initiate the release of any available portion of the adhesive area and then to gradually release a progressively wider band or area of the flap from adhesion. This method of opening is difficult and tedious and results in excessive force being employed to effect opening of the package, pouch or envelope. Such force often results in actual tearing of the body of the envelope and damage to the contents therein. Therefore, a natural tendency is to employ mechanical aids such as sharpened letter openers, scissors, or a knife to assist in cutting or tearing open the package. Use of such mechanical aids also causes damage to the envelope contents in the form of slits, cuts, tears and the like.
Accordingly, it is one object of the present invention to provide a means for opening a sealed envelope, including the types described above, which allows for ease of opening while affording greater protection for contained documents. The notched envelope described herein provides such opening means by enabling the person opening the envelope to easily and firmly grasp onto the flap for subsequent removal of same along a narrow band or area of adhesive and a tear axis.
Yet another object of this invention is to provide a tamper evident package for the preservation of evidence. A current method of providing such protection is to place a signed and dated sticker or seal over the openable portion of an evidence preservation packet. However, such seals may be defeated allowing undetected tampering with the evidence in the packet. The notched envelope described herein provides an improved evidence protection package which responds to any opening force along a tear axis by creating permanent striations and crimped regions in the envelope material indicative of any opening attempt.